Aluminum and polyanion-doping to improve structural and moisture stability of Ni-rich layered oxides for lithium-ion batteries

Ni-rich layered materials LiNi0.8Co0.1Mn0.1O2 attracts extensive interest to build high-performance lithium-ion batteries, but ground challenges, e.g., unfavorable phase transfer and interfacial parasitic reactions during cycling, especially after being exposure to the air for a long time, greatly limit their practical utilization. Here, we prove that those issues of Ni-rich layered materials can be alleviated by concurrently incorporating the Al3+ and PO34-, and conduct corresponding comprehensive studies to explore mechanisms of the enhanced electrochemical performances. It is suggested that the phase transition (H2 to H3) that related to the lattice contraction can be suppressed after Al3+ and PO34- co-doping, leading to improved cycling stability. Additionally, the co-doping successfully mitigates the chemical reaction between the Ni-based oxides and the ambient air, significantly improving the reversibility of lithium intercalation and charge transfer kinetics against long-time storage. Specifically, the Al3+ and PO34- co-doped material maintains 94.1% capacity retention of 150 cycles before storage, and 73.6% capacity retention of 100 cycles after being stored in ambient air for 30 days, which is much better than that of the undoped one. The substitution of Al3+ and PO34- in LiNi0.8Co0.1Mn0.1O2 material is favorable for stabilizing the layered structure against the undesired phase transition of H2 to H3 as well as the contamination of ambient air.